Machines, including construction, on-highway, and agriculture vehicles, have a main power source for moving the machine, powering a tool, or driving other operations. The main power source usually includes an internal combustion engine, such as a diesel engine, a gasoline engine, a gaseous fuel-powered engine, or any other type of engine. These engines include pistons moving in cylinders causing combustion, the pistons being retained in an engine block. A cylinder head typically caps the engine block. The engine also typically includes a cylinder head gasket forming a seal between the cylinder head and the engine block. Each cylinder typically includes a fire ring providing a combustion seal. In resisting the force from engine combustion, transferred from the cylinders into the head, the cylinder head must resist very high stresses. Providing stress slots in the head between the cylinders is one technique for relieving this stress.
Providing stress slots in the cylinder head, though, creates a new problem. While providing flexibility for the head to expand or contract, thereby relieving stress, the stress slots simultaneously reduce the capacity of the cylinder head gasket for supporting the fire rings between cylinders. The stress slots allow for too much movement in the head gasket, which decreases support for the fire rings. When the cylinder head gasket extrudes into the slots, the fire rings take more stress than intended, resulting in a higher rate of fire ring blow-outs between the cylinders. Essentially, the problem of high stress in the cylinder head is mitigated at the expense of an increased rate of fire ring blow-outs. Since a higher rate of fire ring blow-outs has been considered tolerable in view of the advantage of stress relief in the cylinder head, the related problems of stress relief in the cylinder head and fire ring blow-outs have not been simultaneously solved.
One system for reinforcing a head gasket is disclosed in U.S. Pat. No. 4,998,741 (the '741 patent) issued to Udagawa on Mar. 12, 1991. The '741 patent discloses a cylinder head gasket comprising an upper plate, a middle plate, and a lower plate. The cylinder head gasket includes a plurality of holes corresponding to the cylinders of the engine. At least one dividing area is located on the cylinder head gasket between the cylinder holes, this area including a reinforcing bead along the longitudinal direction thereof. The reinforcing bead is provided on the upper plate of the cylinder head gasket to prevent creep relaxation of the upper plate.
Though the '741 patent provides a technique for preventing relaxation in the cylinder head, it does not adequately address the problem of stress relief. While preventing expansion and contraction, which may contribute to protecting against fire ring blow-out, the '741 patent overlooks the related problem of high stresses being attracted in the head by the reinforcing beads. A solution is required that simultaneously solves the related problems of high head stresses and fire ring blow-out, rather than mitigating one problem at the expense of worsening the other.
The cylinder head of the present disclosure solves the dual problems set forth above.